The first vertebrates to fly were pterosaurs, dominating the skies 150 million years ago. Although they reigned absolute above ground, their origin still remained hazy – now, it is known that these colossal wings are the evolution of a small terrestrial biped, the lagerpetid.
The fossil record of pterosaurs is full of gaps not yet filled – Caelestiventus hanseni, their oldest known ancestor, dates back 220 million years and already exhibited all the requirements for flying.
“Pterosaurs fossils that did not have flight mechanisms were never found,” said the lead author of the study published in Nature, Argentine paleontologist Martín Ezcurra, of the Museo Argentino de Ciencias Naturales Bernardino Rivadavia.
In the 1980s, studies confirmed that these dinosaurs resembled birds: they flapped their wings (and not just glided) and walked on their hind legs. At the same time, the hypothesis arose that their closest relatives would be the lagerpetids. Everything fit the evolutionary tree, but there was no evidence to support this hypothesis.
They lived between 237 and 210 million years ago; its size varied between ten centimeters to one meter and its weight must not exceed five kilos. Its fossils are difficult to find (the majority, of later members) and are spread over Brazil, Argentina, USA and Madagascar.
“Lagerpetids are the closest known relatives, in evolutionary terms, to pterosaurs. Although they did not fly, they had some anatomical characteristics – in the jaw, brain, inner ear and teeth – similar to those of pterosaurs ”, the study coordinator, paleontologist Max Langer, from the University of São Paulo (USP) told Revista Pesquisa Fapesp ).
To reach this conclusion, the international team of paleontologists examined dozens of fossils around the world. The work is not new; over the past 15 years, five research groups from six countries and three continents have come together to try to fill in the gaps still open in the evolutionary history of the pterosaur.
The recent identification of skulls and forelimbs similar to those of pterosaurs has prompted the revision of the family tree. The use of advanced techniques, such as micro-tomographic scanning (µCT) allowed to reconstruct the brain and the sensory systems of lagerpetids.